From:	newsham AT lava DOT net (Tim Newsham)
Subject:	Re: cygwin.dll src question: fork()
30 Oct 1997 01:40:39 -0800 :
Message-ID:	<m0xQqGv-0010yIC.cygnus.gnu-win32@malasada.lava.net>
References:	<EItyoH DOT 6sy AT bbc DOT com>
Mime-Version:	1.0
To:	cgf AT bbc DOT com
Cc:	gnu-win32 AT cygnus DOT com

> >At the time when cygwin_fork_helper1() returns isn't the
> >child's state already a copy of the parent's state?
> 
> No, actually, it isn't.  The setjmp and longjmp are used to move the
> current execution point into the appropriate point in the cygwin_fork_helper1
> function to emulate a true UNIX fork().
> 
> What happens is that to emulate a fork, the parent process starts the
[...]
> extends the stack to hopefully insure that the stack is large enough to
> duplicate the parent, and longjmps to the child portion of the
> cygwin_fork_helper1 routine.  There it wakes up the parent and sleeps
> itself.

um..  this is a completely different setjmp/longjmp pair.
The setjmp that is jumped to from crt0 is in the cygwin_fork_helper1()
function.  The __fork() function has its own setjmp/longjmp
pair that seems to add no extra functionality.  Perhaps some sort
of legacy from fork implementations of past.

> http://www.bbc.com/	cgf AT bbc DOT com			"Strange how unreal

                                             Tim N.
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